Poltergeist: The Legacy - Season 1 - Eps 20: The Signalman
A psychic/supernatural occurence debunker and physicist, Dr. David Praeger, is working for the army at an old railway station & tunnel in Powderwash, Colorado. The army is planning on opening a nerve weapon disposal site nearby and he is there to find out what causes the magnetic fluctations in the area. While investigating he starts seeing the 'ghost' of a signalman telling him to 'pull the switch'. Alex finds out where he is after dreaming that he is in danger and, as much as they dislike the man's work the Legacy go to try and save him.
About Poltergeist: The Legacy

Title: Poltergeist: The Legacy
First Air Date: 1996-04-21
Last Air Date: 1999-11-12
Status: Ended
Rating: 6.1/10 (from 33 votes)
Language: EN
Seasons: 4
Total Episodes: 88
Network: Showtime
Genres: Sci-Fi & Fantasy
Production Companies: Trilogy Entertainment Group
Synopsis
The adventures of the members of a secret society known as the Legacy and their efforts to protect humankind from occult dangers.
Cast

Derek de Lint
Derek Rayne, Ph.D.

Martin Cummins
Nick Boyle

Helen Shaver
Rachel Corrigan, MD

Robbi Chong
Alexandra Moreau

Kristin Lehman